The Insteon light switch can replace any light switch in your home and then be "connected" or "controlled" by any other Insteon controller. this allows any Insteon switch to control other Insteon switch allowing you to make any two or more circuits "connected." need to have both ends of a hallway control the hall light? turn on the front lawn light from inside your bedroom so you can look out the window and see what's up? this is the simplest answer and requires no new wires to be run!
here's a neat trick! let's say you want to add a switch in the bedroom to control all the lights in the house but you don't want any other fancy control stuff to do it. you can simply add on a switch to the existing switch! how? well each switch has the wiring you need to add the insteon switches into your home you can easily add an Insteon switch next to an existing switch and then jump the wires over to it. now you have your regular switch and a smart switch that can be "connected" to do any of your insteon tasks in the house! Of course there are several other ways to do this with remotes and even your cell phone, but for situations that might require a simple operation like elderly or children, this is a great solution.